JP4960140B2 - Inductive detection type rotary encoder - Google Patents

Description

  The present invention relates to an inductive detection type rotary encoder that measures the rotation angle of an object using magnetic flux coupling between wirings provided on a rotor and a stator.

  The rotary encoder includes a stator in which a transmission winding and a reception winding are disposed, and a rotor in which a magnetic flux coupling winding capable of being magnetically coupled with these is disposed (see, for example, Patent Document 1). In such a rotary encoder, it is required to further reduce the wiring pitch of the receiving windings in response to a request for downsizing a micrometer or the like on which the rotary encoder is mounted and a request for higher accuracy. Further, when forming an absolute encoder capable of measuring the absolute amount of displacement, it is necessary to form a plurality of tracks on the rotor, and further miniaturization is required.

However, when the wiring pitch of the receiving winding is miniaturized, it is inevitable that the wiring shape is distorted from an ideal shape (for example, a sine wave shape) in order to avoid a wiring short circuit. Such wiring distortion causes a harmonic signal that causes an error in the detection signal.
Japanese Patent Laid-Open No. 10-213407

  An object of the present invention is to provide a highly accurate inductive detection type rotary encoder that does not cause an error based on a harmonic signal even when the wiring pitch is miniaturized.

An inductive detection type rotary encoder according to the present invention includes a stator, a rotor that is rotatable about a rotation axis and disposed opposite to the stator, a transmission winding disposed on the stator, and a rotor. A magnetic flux coupling winding that is formed so that a distance from the rotating shaft changes in a substantially sinusoidal shape and can be magnetically coupled to the transmission winding, and a distance from the rotating shaft on the stator changes in a substantially sinusoidal shape. to so formed and a receiving coil for detecting the magnetic flux generated by said magnetic flux coupling, the receiving Shinmakisen includes a first conductor disposed on the upper layer of the interlayer insulating film, the interlayer insulating film A plurality of contacts in a radial direction of the stator, including at least a second conductor disposed in a lower layer, and contacts formed in the interlayer insulating film for connecting the first conductor and the second conductor; Wherein the first conductor or the second conductor sandwiched region is characterized by being formed so as to have a distorted shape from the substantially sinusoidal in the direction in which the distance increases from the contact.

  According to the present invention, it is possible to provide a highly accurate inductive detection type rotary encoder that does not cause an error based on a harmonic signal even when the wiring pitch is miniaturized.

  Next, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a front view of a digital micrometer 1 equipped with an inductive detection type rotary encoder according to an embodiment of the present invention. A thimble 5 is rotatably attached to the frame 3 of the micrometer 1. The spindle 7 serving as a measuring element is rotatably supported inside the frame 3.

  One end side of the spindle 7 protrudes to the outside, and this one end comes into contact with the object to be measured. On the other hand, a feed screw (not shown in FIG. 1) is cut on the other end side of the spindle 7. This feed screw is fitted into a nut in the thimble 5.

  In this configuration, when the thimble 5 is rotated in the forward direction, the spindle 7 moves forward along the axial direction of the spindle 7, and when the thimble 5 is rotated in the reverse direction, the spindle 7 moves backward along the axial direction of the spindle 7. The frame 3 is provided with a liquid crystal display unit 9 that can display the measurement value of the micrometer 1.

FIG. 2 is a cross-sectional view of the inductive detection type rotary encoder 11 according to the embodiment of the present invention incorporated in the micrometer 1 of FIG.
The rotary encoder 11 includes a rotor 13 and a stator 15 disposed on one surface side of the rotor 13 so as to face the rotor 13. The rotor 13 is fixed to an end surface of a cylindrical rotor bush 19. The spindle 7 is inserted into the rotor bush 19. The stator bush 21 is fixed to the frame 3.

  A feed screw 23 is formed on the surface of the spindle 7 to be fitted into a nut disposed inside the thimble 5 of FIG. Further, a key groove 25 is dug on the surface of the spindle 7 along the longitudinal direction of the spindle 7 (that is, the forward and backward direction of the spindle 7). The key groove 25 is fitted with the tip of a pin 27 fixed to the rotor bush 19. When the spindle 7 rotates, the rotational force is transmitted to the rotor bush 19 via the pin 27 and the rotor 13 rotates. In other words, the rotor 13 rotates in conjunction with the rotation of the spindle 7. Since the pin 27 is not fixed to the key groove 25, the rotor 13 can be rotated without moving the rotor 13 together with the spindle 7.

  Details of the configuration of the inductive displacement detector 11 will be described with reference to FIG. FIG. 3 is an enlarged cross-sectional view of the rotor 13 and the stator 15 described in FIG. The rotor bush 19 and the stator bush 21 are not shown in FIG.

  The stator 15 includes a transmission winding 31 and a reception winding 32. The transmission winding 31 is used to flow a transmission current whose current direction changes periodically, and to provide a magnetic field generated thereby to a magnetic flux coupling winding 41 (described later in detail) formed on the rotor 13. The reception winding 32 is used for flowing an induced current generated by the magnetic flux coupling based on the induced current generated in the magnetic flux coupling winding 41 due to the magnetic flux coupling between the transmission winding 31 and the magnetic flux coupling winding 41. It is.

  The stator 15 includes an insulating substrate 33. Then, three layers of interlayer insulating films 34 to 36 are deposited in this order on the insulating substrate 33. The transmission winding 31 is formed on the interlayer insulating film 34 and covered with the interlayer insulating film 35. The reception winding 32 connects the first conductive film 32A, the second conductive film 32B, and the third conductive film 32C formed on the insulating substrate 33, the interlayer insulating film 34, and the interlayer insulating film 35, respectively, to the contacts C1, C2. (C2 is not shown in FIG. 3). In this case, a three-layer structure of the conductive films 32A to 32C is adopted, but a two-layer structure can be formed, and four or more layers can be formed. A through hole 35 for passing the spindle 7 is provided in the center of the stator 15.

  On the other hand, the rotor 13 has the magnetic flux coupling winding 41 as described above. The magnetic flux coupling winding 41 generates an induced current based on a magnetic field generated by the transmission current flowing through the transmission winding 31. The rotor 13 includes an insulating substrate 42. The magnetic flux coupling winding 41 is formed on the insulating substrate 42 and covered with an insulating film 43. A through hole 47 for passing the spindle 7 is provided at the center of the rotor 13.

  FIG. 4A is a plan view of the stator 15. As shown in FIG. 4A, the transmission winding 31 is formed in an arc shape around the rotation axis (center of the spindle 7). The shape of the transmission winding 31 may be, for example, a shape in which a plurality of rectangular coils are arranged in addition to the arc shape shown in FIG. 4A.

  On the other hand, the reception winding 32 includes three sets of substantially sinusoidal wirings 32-1, 32-2, and 32-3 having different phases from each other on the outer periphery thereof. As an example, the shape of one wiring 32-1 is shown in FIG. 4B. As shown in FIG. 4B, the wiring 32-1 is formed by forming a wiring whose distance from the center of the rotation axis changes in a substantially sinusoidal shape along the circumference over the entire circumference. It is formed by forming over one circumference. For this reason, the wiring 32-1 has a plurality of closed loops U1. An induced current based on a magnetic field generated by the induced current of the magnetic flux coupling winding 41 flows through the closed loop U1, and the rotation amount of the rotor 13 can be calculated by detecting this. The wirings 32-2 and 32-3 have the same shape, but are formed at positions where the wiring 32-1 is rotated by a predetermined angle θ about the rotation axis. The angle θ is θ = λ / 3 when the rotation angle of the two closed loops, that is, when one period is λ.

As described above, receiving Shinmakisen 32, the first conductive film 32A of the three layers which are insulated separated by an interlayer insulating film 34 to 36, the second conductive film 32B, connecting the third conductive film 32C by the contact It is formed by doing.

  As shown in FIG. 5, the first conductive film 32 </ b> A is a conductive film corresponding to the left half portion of one cycle of the substantially sinusoidal wiring. On the other hand, the second conductive film 32B is a conductive film corresponding to the right half of one cycle of the substantially sinusoidal wiring. Further, as shown in FIG. 7, the third conductive film 32C is a conductive film corresponding to the end portions of the wirings 32-1, 32-2, and 32-3. Wirings 32-1, 32-2, and 32-3 are formed by connecting these half-cycle wirings and end wirings through contacts C1 and C2. Each of the conductive films 32A to 32C is formed in a substantially sine wave shape, but in the vicinity of the contact C1 or C2, a distorted shape is given in comparison with the sine wave shape in order to avoid a short circuit. This point will be described later.

  FIG. 8A is a plan view of the rotor 13. As shown in FIG. 8, the magnetic flux coupling winding 41 formed on the rotor 13 has a closed loop shape in which the distance from the rotation axis changes in a substantially sinusoidal shape. Since it is a simple closed loop as shown in FIG. 8, symmetry is ensured. In FIG. 8, a sinusoidal loop having four cycles at intervals of 90 ° is given to the magnetic flux coupling winding 41. This period need not be limited to 4 periods, and may be 3 periods or less (or 1 period) or 5 periods or more. By giving such a substantially sine wave shape to the magnetic flux coupling winding 41, it is possible to suppress the influence of distortion in the vicinity of the contacts of the conductive films 32A to 32C described above.

  As a comparative example, FIG. 8B shows a rotor 13 ′ in which another shape of the magnetic flux coupling winding 41 ′ is formed. Unlike the one of FIG. 8A, the magnetic flux coupling winding 41 ′ of the rotor 13 ′ has a rectangular wave shape (gear shape). In FIG. 8B, a loop of 4 cycles at intervals of 90 ° is provided to the magnetic flux coupling winding 41 ′.

  9A shows that the rotor 13 shown in FIG. 8A is relatively rotatable with respect to the stator 15 shown in FIG. 4 (the reception winding 32 has a shape distorted with respect to the sine wave shape). The error [deg] of the measured value at each angle in the case of one rotation (0 to 360 °) is shown. On the other hand, FIG. 9B shows that the rotor 13 shown in FIG. 8B is relatively rotatable with respect to the stator 15 shown in FIG. 4, and the rotor 13 makes one rotation (0 to 360 °) at each angle. The measurement value error [deg] is shown. 9A and 9B, according to the substantially sinusoidal magnetic flux coupling winding 41 of FIG. 8A, the receiving winding 42 has distortion compared to the gear-shaped magnetic flux coupling winding 41 ′ of FIG. 8B. In, the measurement error can be reduced.

  The distortion of the reception winding 32 will be described with reference to FIGS. The first conductive film 32A, the second conductive film 32B, and the third conductive film 32C constituting the reception winding 32 basically have a sine wave shape. However, the first conductive film 32A, the second conductive film 32B, and the third conductive film 32C have distorted shapes that deviate from the sine wave shape in the vicinity of the contacts C1 and C2. This avoids a short circuit failure between the conductive films 32A to 32C and the contacts C1 and C2. Specifically, as shown in the enlarged view in FIG. 10, the conductive films 32 </ b> A to 32 </ b> C pass through a position far from the contact C <b> 1, which is out of the locus of the sine wave (broken line) ( Only the conductive film 32A is shown, but the other conductive films 32B and 23C are the same).

  This distortion will be further described with reference to FIG. FIG. 11 is an enlarged view of the vicinity of two contacts C1 arranged in the radial direction of the stator 15, that is, in the direction of the width L of the track on which the reception winding 32 is formed. Two first conductive films 32A run between the two contacts C1. Since the second conductive film 32B is the same, here, the case of the first conductive film 32A will be described as an example.

Here, the radial width of the track receiving Shinmakisen 32 are formed L, and radius of the contact C1 R1, the width of the first conductive film 32A and W. The interval between the contact C1 and the first conductive film 32A is S.

  In this case, if the wirings 32-1, 32-2, and 32-3 are given a phase difference of θ = λ / 3 and have a substantially sinusoidal shape, the first conductive film 32A is shown in FIG. Thus, it passes through a position of about L / 4 from the upper end or the lower end of each track. For this reason, with respect to the interval S, the following equation holds.

[Equation 1]
S = L / 4-R1-W / 2
In order to avoid a short circuit failure between the contact C1 and the first conductive film 32A and obtain a high yield, the interval S needs to be 0.1 mm or more. However, L = 0.8 mm is required due to the demand for miniaturization and high resolution of the inductive detection type rotary encoder, and W and R1 are W = 0.1 mm and R1 = 0.125 mm. Currently the minimum value.

  For this reason, according to [Equation 1], the interval S is less than S = 0.025 mm, which makes it difficult to manufacture.

  Therefore, in the present embodiment, as shown in FIG. 10, the first conductive film 32A is distorted from a sinusoidal shape near the contact C1. That is, S <L / 4−R1−W / 2 is established even under the above conditions of L, R1, and W.

  Although the embodiments of the invention have been described above, the present invention is not limited to these embodiments, and various modifications and additions can be made without departing from the spirit of the invention.

1 is a front view of a digital micrometer 1 equipped with an inductive detection type rotary encoder according to an embodiment of the present invention. It is sectional drawing of the induction | guidance | derivation detection type | mold rotary encoder 11 based on embodiment of this invention integrated in the micrometer 1 of FIG. FIG. 3 is an enlarged cross-sectional view of a rotor 13 and a stator 15 described in FIG. 2. 3 is a plan view of a stator 15. FIG. The structure of one of the wirings having different phases constituting the reception winding 32 is shown. The structure of the first conductive film 32A of the first layer constituting the reception winding 32 is shown. The structure of the second conductive film 32B of the second layer constituting the reception winding 32 is shown. The structure of the first conductive film 32C of the third layer constituting the reception winding 32 is shown. 3 is a plan view of a rotor 13. FIG. It is a top view of rotor 13 'concerning a comparative example. 8A shows measurement errors when the rotor 13 shown in FIG. 8A is used. The measurement error when the rotor 13 'shown in FIG. 8B is used is shown. The distortion from the sinusoidal waveform applied to the reception winding 32 will be described. The distortion from the sinusoidal waveform applied to the reception winding 32 will be described.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Micrometer, 3 ... Frame, 5 ... Thimble, 7 ... Spindle, 9 ... Liquid crystal display part, 11 ... Rotary encoder, 13 ... Rotor, 15 ... Stator, 19 ... Rotor bush, 21 ... Stator bush, 25 ... Keyway, 27 ... Pin, 31 ... Transmission wiring, 32 ... Reception winding, 32A ... First Conductive film, 32B ... second conductive film, 32C ... third conductive film, C1, C2 ... contact, 33, 44 ... insulating substrate, 34,35,36 ... interlayer insulating film, 37 ... through hole, 43 ... insulating film.

Claims (2)

A stator,
A rotor that is rotatable about a rotation axis and disposed opposite the stator;
A transmission winding disposed on the stator;
A magnetic flux coupling winding formed on the rotor such that a distance from the rotation shaft changes in a substantially sinusoidal shape and capable of being magnetically coupled to the transmission winding;
A receiving winding configured to detect a magnetic flux generated by the magnetic flux coupling winding formed on the stator so that a distance from the rotating shaft changes in a substantially sinusoidal shape;
The receiving Shinmakisen includes a first conductor disposed on the upper layer of the interlayer insulating film, a second conductor disposed in the lower layer of the interlayer insulating film, for connecting the first conductor and the second conductor At least a contact formed on the interlayer insulating film,
The first conductor or the second conductor in the region sandwiched between the plurality of contacts in the radial direction of the stator is formed to have a shape distorted from the substantially sinusoidal shape in a direction in which the distance from the contact increases. An inductive detection type rotary encoder characterized by that. The shape before Ki受Shinmakisen, inductive detection type rotary encoder according to claim 1, characterized in that distorted compared to a sine wave in the vicinity of at least the contact.

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